1. Field of the Invention
The present invention relates generally to an optical disk apparatus. More particularly, the invention is concerned with an optical disk apparatus which is advantageously suited for driving an optical disk having a diameter not greater than 3.5 inches and which can enjoy an excellent portability.
2. Description of the Related Art
The optical disk apparatuses known heretofore are mainly of such a structure in which a spindle motor for rotating an optical disk serving as a medium for storage of information is stationarily mounted and an optical head mechanism or head assembly including an optical head for recording and/or reproducing information on and/or from the optical disk and a laser circuit for emitting a light beam required for the operation of the optical head is caused to move linearly in the direction diametrically of the optical disk by means of a linear actuator.
The optical disk apparatus of the structure mentioned above however suffers from a problem that difficulty is encountered in speeding up the access operation of the optical head assembly to the optical disk because of heaviness of the head assembly. An approach for solving this problem is disclosed in Japanese Unexamined Patent Application Publication No. 85890/1989 (JP-A-1-185890). According to the proposal described in this publication, the optical head assembly is mounted stationarily while the spindle motor for rotating an optical disk is linearly moved relative to the head assembly in the diametrical direction of the disk by a linear actuator realized by using a voice coil. However, in this known apparatus, no consideration is paid to implementation of the apparatus in a miniature size of a thin and light weight structure capable of withstanding vibration. Thus, the optical disk apparatus mentioned above can not evade a shortcoming concerning the portability among others.
Another disadvantage of the optical disk apparatuses known heretofore is seen in that significant power consumption is involved because the optical disk is rotated by the spindle motor even when the apparatus is in the inactive state, performing neither recording nor reproduction of information on or from the optical disk.
In recent years, studies and developments aiming for high structural integration density and high data transfer rate of the optical disk apparatuses are reported, and the rotation speed of the spindle motor used therefore shows an yearly increase. However, this means in turn that the power consumption of the disk apparatus increases correspondingly. Under the circumstances, there exists a demand for decreasing the power consumption of the optical disk apparatuses particularly of those operated by an onboard battery.